1. The Field of the Invention
The invention relates to the field of communication along a fiber optic channel. More specifically, the invention relates to active fiber optic components or photonic devices such as transceivers, transmitters and receivers that can be used with sub-millimeter diameter interconnect systems.
2. The Relevant Technology
Fiber optic transceiver modules, also known as optoelectronic transceivers, transmit and receive data by the means of optical signals. Such transceivers provide for the bi-directional communication of signals between an electrical interface and an optical interface. A fiber optic transceiver includes a circuit board that contains at least a receiver circuit, a transmitter circuit, a power connection and a ground connection.
Transceivers and other active fiber optic modules are miniaturized in order to increase the port density associated with the network connection with respect to switches, routers, cabling patch panels, wiring closets, computer I/O and the like. Form factors for miniaturized optical modules such as Small Form Factor Pluggable (“SFP”) that specifies an enclosure about 9.05 mm in height above the PC board by about 13.2 mm in width and having a minimum of 20 electrical input/output connections. In order to maximize the available number of optical transceivers per area, multiple transceiver modules are arranged in rows and columns. Each SFP transceiver module or other active photonic module is plugged into a socket or receptacle.
As the need for bandwidth has increased, high speed optical transceivers have been developed to satisfy this need. The primary markets for this demand for increased bandwidth has been both the local area network (LAN) and the storage area network (SAN) markets. The predominant LAN standard is Ethernet, while the predominant SAN standard is Fibre Channel. Transceivers from speeds of 155 Mb/s up to 10 Gb/s have been introduced that meet these requirements and it is expected that even higher speeds will soon be required.
The initial transceivers were based on 1×9 modules (shown on FIG. 2A) which were soldered onto a host printed circuit board (“PCB”) and utilized duplex SC optical connectors. The need for reconfigurability led to the development of the first hot-pluggable transceivers, known as GBIC (Gigabit Interface Converter), having a footprint on the front panel of a host system that is similar to the 1×9 module, which could be plugged into a powered circuit board in a router, switch, or other such piece of equipment (thus, the term “hot-pluggable.”)
Arrays of these modules could be placed on the edge of a circuit board such that the SC outputs were presented at the output of a switch or router. The dual SC port arrangement limited the minimum size of the ports that could be stacked together. The ferrule of the SC connector is 2.5 mm in diameter. The center-to-center spacing of the dual SC port is 12.7 mm, and the width of the dual SC port is 26 mm. The height is 9.4 mm above the PC board surface.
Shortly thereafter, the need to increase the density of optical ports resulted in the introduction of both the Small Form Factor soldered (SFF) and Small Form Factor pluggable (SFP) transceivers. The SFF and SFP transceivers reduced the size of the modules in half in the horizontal direction by replacing the optical interface with duplex LC connectors, which are half the size of SC connectors, as shown in FIG. 2B. The ferrule of the LC connector is 1.25 mm in diameter. The center-to-center spacing of the duplex LC port is 6.1 mm, and the width of the dual LC port is 13.2 mm. The height of the dual LC port is 9.05 mm above the PC board surface.
The large success of fiber optic networks based on these described active fiber optic transceivers has increased the demand for even higher port density that can only be met by transceivers and other active components that are even smaller than those currently available. Until now, no known optical interface has been able to successfully address this need for transceivers of smaller size. In such high density applications, the components are too small to connect and disconnect with one's fingers. The present invention solves that problem with its new transceiver, as shown in FIG. 1, which is based on a new fiber optic interface which is about 3 times smaller than the standard SFF/SFP form factor, as shown on FIG. 2C. In turn this interface is built around the ferrule with diameter substantially less than 1.25 mm.
To convert electronic data to optical data for transmission through a fiber optic cable, a transmitter optical subassembly (“TOSA”) is typically used. A driver integrated circuit converts electronic data to drive a laser diode or an LED in a TOSA to generate the optical signal or data.
To convert optical data to electronic data, a receiver optical subassembly (“ROSA”) is typically used. The ROSA typically includes a photo diode that, in conjunction with other circuitry converts the optical data to electronic data. To communicate through fiber optic cables, usually both a TOSA and a ROSA are needed. Combining both a TOSA and a ROSA into a single assembly along with electronic devices and circuits, results in a transceiver. Typical transceiver designs combining discrete TOSAs and ROSAs cannot have their footprint further reduced in size because of the standard LC connector interface. Further, even if a smaller optical connector interface were available, TOSAs and ROSAs using standard packaging technology would not be able to be substantially reduced in size because smaller transistor outline (TO) packages which contain the optoelectronic die (lasers and photo detectors) are not available. It is difficult to reduce the size of these TO cans further as the glass feed throughs for the electrical leads cannot be further reduced in size.
Accordingly, there is a need for super miniature active fiber optic modules designed for high density applications especially in data and telecommunication electronic equipment. Generally, three major technical challenges in achieving this goal are: (1) providing substantially smaller passive interconnect systems that provide the needed functionality, (2) developing the substantially smaller active fiber optic modules that provide the necessary function, and, (3) achieving compatibility of the new active modules with the new passive interconnect system.